I would want out of this job too, for many reasons that spell trouble in short order.

If you don't have the money necessary to facilitate an addition that is 'properly' added to your home you shouldn't do the addition.

It is hard to advise you without seeing the details of the duct work. In general I suggest you terminate the duct work as close to the main trunk line as much as possible. Filling in vents with spray foam is a bad idea in my opinion.

If you don't have confidence in the HVAC contractor, and he is looking to get out of the job, then you should find another contractor.

Little good come's out of jobs where reluctant contractors are paid to complete the work.

I agree. We expressed our concern to our contractor and they've basically pushed this company to finish up what they started. We are going to bring in another company to check out the work. We would have rather have paid more to be sure it was done right from the beginning. Would have caused a lot less stress.

General contractors know little about HVAC and are going to subcontract the work to the lowest bidder. It is unfortunate you have to hire a second company to monitor the first. You are spending a lot of money on the addition so you are doing the right thing by bringing in skilled HVAC people.